The present invention relates to an electrical switchgear and, more particularly, to an arc-resistant enclosure for a switchgear and a ventilation system therefor.
Internal arc faults in an arc-resistant switchgear enclosure generate high pressures due to expanding gasses. These gasses are vented from the switchgear enclosure into an exhaust plenum. Typically, there is a vent opening between the breaker compartment and the vent compartment and a flap can cover the opening. The opening from the breaker compartment to the vent chamber is normally open to let the arc gasses escape from the breaker compartment into the vent chamber. The normally open configuration is required for high amperage switchgear (2000 A & above) in order to dissipate the heat generated in the breaker compartment.
For a Type 2C switchgear construction, as defined in the arc-resistant testing standard IEEE C37.20.7, no arc gasses are allowed to penetrate a compartment once they leave the one where the arc fault is created. This is a technically challenging requirement to meet. When the arc gasses flow through an arc chamber to the exhaust plenum, the opening to a breaker compartment (excluding the one where a fault may have occurred) must be closed so that no gasses will enter. It is not possible to have sealed compartments to prevent such entry of gasses since it would lead to unacceptable temperature rise within the compartments.
Thus, there is a need to provide an improved switchgear enclosure that ensures that heat convection can occur under normal operating conditions and yet ensure that compartments become isolated when the arc gasses flow into the arc chamber due to arc faults in other compartments.